1. Technical Field
The present invention relates to electrical devices which include a housing and electrical components received in the housing.
2. Description of the Related Art
For example, in electrical vehicles and hybrid vehicles, there are used electrical devices such as a DC-DC converter and an inverter; those electrical devices include electrical components that form an electric power supply circuit and a housing that receives the electrical components therein. Further, the housing generally has a main body and a lid both of which are electrically conductive, so as to electromagnetically shield the electrical components received in the housing. Consequently, electromagnetic noise generated by the electrical components can be prevented from leaking outside of the housing; the electrical components include, for example, at least one of a transformer, a choke coil and switching elements. As a result, it is possible to prevent the electromagnetic noise generated by the electrical components from influencing other electrical devices or components located in the vicinity of the electrical device.
Furthermore, in the housing, there may be a gap formed between the main body and the lid; thus, the electromagnetic noise generated by the electrical components may leak outside of the housing via the gap. However, in this case, if the main body and the lid are electrically connected with each other, it is still possible to electromagnetically shield the electrical components received in the housing. Therefore, in an electric power supply device disclosed in Japanese Patent No. 4624881, the lid has a plurality of raised portions (or protrusions) formed therein; via the raised portions, the main body and the lid are in partial contact with each other.
However, in the electric power supply device disclosed in the patent document, the raised portions are formed on the inner surfaces of sidewalls of the lid so as to abut against the outer surfaces of sidewalls of the main body. That is, all the directions of contact between the main body and the lid at the raised portions are perpendicular to the direction of fixing the lid to the main body. Consequently, it may be difficult to secure high contact pressure between the main body and the lid at the raised portions, and thus the contact resistance between the main body and the lid may tend to be large. As a result, the effect of electromagnetically shielding the electrical components by the housing may be lowered.
To solve the above problem, one may consider setting the distances between facing pairs of the sidewalls of the lid to be small and thereby making the contact pressure between the main body and the lid at the raised portions large. However, in this case, with the small distances between the facing pairs of the sidewalls of the lid, it would be difficult to fit the lid onto the main body, thus lowering the productivity. In addition, it would be easy for the outer surfaces of the sidewalls of the main body to be scratched or abraded by the raised portions of the lid during the fitting of the lid onto the main body.
Moreover, with the directions of contact between the main body and the lid at the raised portions perpendicular to the direction of fixing the lid to the main body, it may be difficult to stabilize the fixed state of the main body and the lid. Consequently, rattling noise may be easily caused by vibration between the main body and the lid.
Furthermore, in the electric power supply device disclosed in the patent document, the lower ends of the sidewalls of the lid are positioned close to a bottom wall of the main body. Therefore, even with gaps formed between the inner surfaces of the sidewalls of the lid and the outer surfaces of the sidewalls of the main body, it may be difficult to discharge heat generated by the electrical components outside of the housing.
More specifically, in the case of dissipating the heat generated by the electrical components via heat convection, the heat is discharged outside of the housing by discharging the high-temperature air in the internal space of the housing to the external environment via the gaps formed between the inner surfaces of the sidewalls of the lid and the outer surfaces of the sidewalls of the main body. However, with the lower ends of the sidewalls of the lid positioned close to the bottom wall of the main body, the exits of the gaps are also positioned close to the bottom wall of the main body. Consequently, it may be difficult for the high-temperature air, which ascends in the internal space of the housing, to be discharged outside of the housing via the gaps. As a result, it may be difficult to secure a high performance of the electrical device for dissipating the heat generated by the electrical components.